Laser diode (LD) modules capable of producing high-power and high-intensity laser beams by coupling a plurality of laser beams emitted from a plurality of laser diodes into optical fibers have conventionally been used widely. For example, Patent Document 1 discloses a micro-optical device in which (i) a plurality of laser beams parallel to each other are reflected by a prism so that a direction of travel of the laser beams are converted, and (ii) the laser beams are then focused to be coupled into an optical fiber.